Plasma processing is an essential technique for manufacturing semiconductor devices. In recent years, due to an increasing demand for high-integration and high-speed of LSI (Large-Scale Integration), design rules for semiconductor devices constituting LSI have changed to miniaturize the device, and semiconductor wafers have been enlarged in size. Accordingly, a plasma processing apparatus has been required to allow such miniaturization of semiconductor devices and enlargement of the semiconductor wafers.
However, in a conventional parallel plate type or inductively coupled plasma processing apparatus, it is difficult to perform uniform and high-speed plasma processing for semiconductor wafers.
In this regard, an RLSA (a registered trademark) microwave plasma processing apparatus has received attention. The RLSA microwave plasma processing apparatus uniformly generates high-density surface wave plasma having a low electron temperature.
The RLSA microwave plasma processing apparatus is provided with a radial line slot antenna, i.e., a planar slot antenna having a plurality of slots formed, with a predetermined pattern in the upper portion of a chamber as a microwave radiation antenna emitting microwaves for generating surface wave plasma. In the RLSA microwave plasma processing apparatus, the microwaves from a microwave source is guided to be radiated into a chamber kept at vacuum through the slots of antenna and a dielectric microwave transmission plate provided below the slots. By an electric field of the microwaves, surface wave plasma is generated in the chamber and target objects such as semiconductor wafers are processed by the plasma.
In such a RLSA microwave plasma apparatus, in order to adjust plasma distribution, a plurality of antennas different in slot shape, pattern and the like should be prepared for a replacement of the antenna. This preparation may be very troublesome.
In contrast, a plasma source has been disclosed in the related art in which one microwave is divided into a plurality of microwaves to and distributed to a plurality of microwave introduction mechanisms having a planar antenna as described above are installed. In the plasma source, the microwaves radiated therefrom are guided into a chamber and spatially synthesized in the chamber.
As the microwaves are spatially synthesized using the plurality of microwave introduction mechanisms, the microwave being introduced from each of the microwave introduction mechanisms can be individually adjusted in phase or amplitude and thus a plasma distribution can be relatively easily adjusted.
In addition, an arrangement of a plurality of microwave introduction mechanisms has been suggested to secure uniformity of a plasma distribution in the related art.
In the related art, a dielectric microwave transmission window (microwave transmission member) is installed in each microwave introduction mechanism of the ceiling wall of the chamber and the microwaves are radiated into the chamber through the microwave transmission window. In such a configuration, however, since the plasma is not sufficiently generated, a large number of microwave radiation units are needed in order to obtain uniform plasma.